This invention relates generally to recording head sliders of disk drive assemblies. More particularly, it relates to trapezoidal-shaped silicon sliders.
Hard disk drives utilizing magnetic data storage disks are used extensively in the computer industry. A head/disk assembly typically includes one or more commonly driven magnetic data storage disks rotatable about a common spindle. At least one head actuator moves a plurality of magnetic read/write heads radially relative to the disks to provide for reading and/or writing of data on selected circular concentric tracks of the disks. Each magnetic head is suspended in close proximity to one of the recording disks and supported by an air bearing slider mounted to the flexible suspension. The suspension, in turn, is attached to a positioning actuator.
During normal operation, relative motion between the head and the recording medium is provided by the disk rotation as the actuator dynamically positions the head over a desired track.
The relative motion provides an air flow along the surface of the slider facing the medium, creating a lifting force. The lifting force is counterbalanced by a known suspension load so that the slider is supported on a cushion of air. Air flow enters the leading edge of the slider and exits from the trailing end. The head resides toward the trailing end, which tends to fly closer to the recording surface than the leading edge.
Conventional magnetic recording head sliders are typically made from wafers of a two-phase ceramic, TiC/Al2O3, also called Al-TiC. After the thin film processing to prepare the recording heads is performed on the Al-TiC wafers, the sliders are then formed. The sliders are fabricated by cutting, grinding and lapping the wafer made of the above material. This involves a series of shaping and polishing operations, and also the formation of an air bearing, usually using dry etching, on the polished surface.
Normally, magnetic recording head sliders are formed to have a rectangular prism shape, having a rectangular footprint. Occasionally an unwanted process deviation, such as substrate misalignment or uneven lapping pressure, leads to substrate non-rectangularity. Alternatively, sliders have been fabricated having a triangular shape.
The nature of magnetic recording has changed in the last several years from one in which a slider comes to rest on the recording medium, either in a data field or a special landing zone, to one in which a slider is never allowed to come to rest anywhere upon the recording medium. This is accomplished through the use of a xe2x80x9cload/unloadxe2x80x9d device, which is essentially a ramp containing a resting place for the suspension/slider assembly. A metal extension from the suspension is used to hold the assembly in place. One problem with this approach is that as the slider and suspension are swung back onto the disk from the rest position, there is the potential for disk damage as the leading edge of the slider and longitudinal edges contact the disk. To prevent such disk damage, the slider is mounted on the suspension with a positive pitch (the leading edge is higher than the trailing edge with respect to the disk), which requires that the suspension be bent in a particular way. FIG. 1 is a schematic diagram showing a magnetic recording system 100 including a recording medium 102 and a rectangularly shaped slider 104 mounted on a flexure 108 connected to a suspension 106 through a gimbal 110. The flexure 108 is bent to provide a positive pitch xcex8.
U.S. Pat. No. 4,809,103, issued to Lazzari on Feb. 28, 1989, discloses a head slider for magnetic recording on a recording media. The slider is a silicon wafer with a first face parallel to the recording media and a second opposite face parallel to the first face. A flat magnetic head is integrated into the silicon wafer in the first face, and an electronic circuit is integrated in either first or second face. The slider is thinner than a conventional slider. However, there is the potential for damage of the recording media as the edges of the slider make contact with the disk.
An article entitled xe2x80x9cA New Sub-Femto Slider for Mass Production Planar Silicon Headxe2x80x9d by Lazzari et al., published in IEEE Transactions on Magnetics, Vol. 34, No. 4, July, 1998, discloses a slider of triangular shape. The triangularly shaped slider is fabricated by cutting a silicon wafer in three directions. The triangular shape reduces the unused surface of the slider. However, an unwanted process deviation may lead to slider non-triangularity, and there is still the potential for damage of the recording media as the edges of the slider make contact with the disk.
There is a need, therefore, for an improved slider that overcomes the above difficulties.
A recording head slider having a trapezoidal shape is described according to an exemplary embodiment of the present invention. The slider is made of silicon and has a first parallel surface larger than a second parallel surface. The first parallel surface is the surface upon which the recording head is fabricated. The first parallel surface of the slider also includes rounded corners.
The slider further may include longitudinal, through or partially-through holes within its body to reduce the mass of the slider. A pattern of these through or partially-through holes may be used as a slider identification system, as well, in which a reader may identify the slider origin based on the pattern of the holes at the surface. The slider may also include longitudinal grooves, having an arbitrary cross-section, along its slanted side surfaces. These grooves produce non-planar structures along the length of the slider body, allowing more convenient part handling and location. Furthermore, these grooves may also form the basis of a slider identification system, in which the presence or absence of a groove or protrusion along the sides or top of the slider allows its identification with respect to position location within the wafer and/or the wafer identity.
The trapezoidal silicon slider of the exemplary embodiment is incorporated in a recording device. The recording device includes a trapezoidal silicon slider mounted on the suspension, which is suspended above a recording medium. The slider is mounted on the suspension at its first slanted side surface such that a trailing end of the slider, which is the first parallel surface of the slider, is larger than its leading end, which is the second parallel surface of the slider. Therefore, a built-in positive pitch of about 0.6 degree is generated. The leading end of the slider has a rounded leading edge that is advantageous for preventing the damage of a magnetic recording disk when the leading edge contacts the disk during operation. A second slanted side surface opposite the first slanted side surface is an air bearing surface of the slider in the recording device. The longitudinal edges at this air bearing surface are also rounded during the slider fabrication process.
The trapezoidal slider of the exemplary embodiment is fabricated using a commercial deep reactive ion etching (DRIE) technique. A silicon substrate is first provided, upon which the recording head is fabricated using thin film processing. Photoresist masks are then deposited onto a top surface of the silicon substrate. The photoresist masks are patterned with round corners, through holes, and grooves at the sides, producing a slider having a first parallel surface with rounded corners, longitudinal through holes or partially-through holes within the body, and the longitudinal grooves along its slanted side surfaces. Partially-through holes may be generated in the slider body by choosing a maximum diameter or dimension of the pattern in the photoresist used to define the etched area. If this dimension is below a certain level, dependent on the thickness of the wafer to be etched, the etching process is terminated at a point above the bottom of the wafer. Thus, somewhat conical holes may be generated which merely reduce the slider mass, but do not go through the wafer. These may be used to prepare a machine readable slider identification pattern, also. Through careful selection of the process parameters, slightly re-entrant angled etch surfaces are generated during the etching, resulting in a slider with a first parallel surface larger than a second parallel surface and trapezoidal, etched, slanted side surfaces. It should be noted that the DRIE process alluded to here is appropriate for etching Si and much less so for other materials. If it is necessary to remove material overlying the Si substrate in preparation for etching the Si, a means of etching or removing this material other than using DRIE is necessary.
Since it is desirable to have a leading end with rounded edges, a technique is used, based on the DRIE process, to generate the rounded edges. A thin, insulating layer is deposited on the bottom surface of the silicon substrate. The insulating layer is generated by thermally oxidizing or sputter depositing a thin oxide layer on the bottom surface of the silicon substrate. (The thermal oxidation process, performed at relatively high temperature, is only applicable preceding recording head fabrication.) The thickness of the oxide layer is between about 0.05 micron and 1.0 micron, preferably 0.1 micron. Alternatively, the thin insulating layer can be a cured photoresist layer on the bottom surface of the silicon substrate. The thickness of the photoresist layer is between 0.3 micron and 3 micron. An electrically conductive layer is also deposited adjacent to the insulating layer. The conductive layer may be a vacuum-deposited metal layer or it may be a conductive adhesive. Such a conductive adhesive layer is deposited by laminating a thick film or spinning a layer of the conductive adhesive on the silicon substrate after the insulating layer is deposited on the wafer. Alternatively, the conductive layer can be deposited by laminating a thick film or spinning a layer of conductive adhesive on a necessary support substrate, which holds the silicon substrate during the etching process. In both cases the wafer with insulating layer is positioned on the additional substrate, with the conductive adhesive intermediate between the two. In the case where the wafer is metallized, the adhesive need not be conductive.
The rationale for the above structure is that during the DRIE process the species which perform the etching of the Si wafer are ionized and are accelerated toward the bottom of the hole by the fields produced in the DRIE tool. If, at the bottom of an etched hole or trench an insulating region is encountered, the ions generate a charged region which repels much of the ion bombardment. The ions are then deflected toward the bottom edge of the etched hole, causing localized etching or undercutting at this point. This is normally to be avoided, but for the situation where a rounded edge is desired, this process may be used to advantage. After the bottom edge of the hole is rounded, the rounding process is terminated once the insulator at the bottom of the hole is etched away. Thus, when the underlying electrically conductive layer is exposed, the rounding process is completed. The degree of desired rounding determines the desired thickness of the insulating layer.
The trapezoidal-shaped slider of the present invention has a reduced mass compared with a conventional rectangular shaped slider, which improves the mechanical response of the overall seeking/track-following performance in the hard disk drive. Furthermore, the trapezoidal-shaped slider prevents disk damage during operation. The rounded corners and edges generated during slider etching also reduce disk damage during operation. Grooves, formed along the sides or top of the slider during the etching process, allow easier machine gripping of the slider and centerline location of the top surface. Furthermore, these grooves can be used to make up a system which allows identification of the location of the slider position in the wafer, along with the identification of the wafer itself. Such a system allows the slider identity to be imprinted during the DRIE process, rather than during some separate, dedicated process. The pattern of through or partially-through holes on the top of the etched surface can be used for slider identification, as well.